The microelectronics fabrication industry is moving toward smaller geometries in its devices to enable lower power consumption and faster device speeds. As the conductor lines become finer and more closely packed, the requirements of the dielectrics between such conductors become more stringent. New materials having a lower dielectric constant than the dielectric constant for silicon dioxide, the traditionally used dielectric material, are being investigated. Among the dielectric materials that are attaining increased acceptance are spin-on, organic polymers having a dielectric constant of less than about 3.0. Polyarylenes, including polyarylene ethers and SiLK™ semiconductor dielectric (from The Dow Chemical Company), are the primary organic polymeric dielectrics being considered.
The fabrication of microelectronic devices using these new dielectric materials is being reviewed. See, e.g., “Material Research Society (MRS) Bulletin, October 1997, Volume 22, Number 10” To date, however, the polyarylene dielectrics generally have been patterned in the traditional manner using inorganic hardmasks in forming patterns in the dielectric materials. Typically, the polyarylene dielectric is applied to the substrate and cured, followed by vapor deposition of an inorganic hardmask. A pattern is formed in the inorganic hardmask according to standard patterning practices, e.g., application of a photoresist (i.e., softmask), followed by exposure and development of the softmask, pattern transfer from the softmask into the hardmask, and removal of the softmask. Etching of the hardmask is typically done using fluorine based chemistries. The underlying polyarylene dielectric can then be patterned. Deposition conditions must be carefully monitored to assure adequate adhesion between the hardmask and the polyarylene films.
Subsequent to the original priority date claimed by this application, patent publications were made that also discuss various methods and embodiments of dielectric materials, etch stops and hardmasks in fabrication of microelectronic devices.
In WO01/18861 (15 Mar. 2001), after stating the well known concept that layers used as adjacent etchstop and dielectric materials should have substantially different etch selectivities, the applicants teach that an inorganic layer (defined as containing no carbon atoms) should be used as a via level and metal level intermetal dielectric and an organic low dielectric constant material should be used between the inorganic layers as an etch stop material.
In WO00/75979 (14 Dec. 2000), teaches a structure having a first dielectric layer which is an organic polymer and a second dielectric layer over the first layer which is a organohydridosiloxane made by a relatively complex synthesis method.
In addition, U.S. Pat. No. 6,218,078 (Apr. 17, 2001 filed Sep. 24, 1997) teaches the use of a spin on hardmask (only hydrogensilsesquioxane is mentioned) over a low dielectric constant polymer (only benzocyclobutene is mentioned).
Finally, U.S. Pat. 6,218,317 (Apr. 17, 2001 filed Apr. 19, 1999) teaches use of methylated oxide hardmasks over polymeric interlayer dielectric materials. This patent mentions the benefits that both hardmask and ILD can be spin-coated.